In Darrieus Wind Turbines, the vertical rotor shaft is supported at its lower end and arranged to rotate a gear or other structure connected to a generator for generating electricity, or for powering equipment when the shaft rotates. This support is normally in the form of a ball or roller thrust bearing through which high forces are transmitted from the rotating shaft, through to the stationary supporting foundation. This bearing has a limited life and consumes energy in the form of friction.
In emergencies, the wind turbine must be shut down as quickly as possible. In this case, the angular speed must be reduced to zero or to an angular speed at which the emergency ceases to affect the operation of the wind turbine, and this must all be done almost instantaneously. No "fail safe" method of achieving this result has been achieved.
In addition, the upper end of the vertical shaft of the Darrieus Rotor is normally supported by guy wires. The length of these cables fluctuates with temperature varying the tension in the wires. Consequently, the natural frequency of the wires is affected which can from time to time, cause the wires to sympathetically vibrate by the action of the rotor and become a hazard to the operation of the wind turbine.
It is therefore an object of this invention to provide a wind turbine, gear box assembly, sub-assemblies and components therefor, which overcome the aforementioned deficiencies of the prior art structures.
Further and other objects of the invention will be realized by those skilled in the art from the following summary of the invention and detailed description of preferred embodiments thereof.